The invention relates generally to medical imaging systems, and more particularly, to Positron Emission Tomography (PET) scanners.
PET scanners typically generate images depicting the distribution of positron-emitting nuclides in patients. The positron interacts with an electron in the body of the patient by annihilation, and then the electron-positron pair is converted into two photons. The photons are emitted in opposite directions along a line of response. The annihilation photons are detected by detectors that are placed on both sides of the line of response on the detector ring. The image is then generated based on the acquired emission data that includes the annihilation photon detection information.
In PET scanners the image quality depends on the image statistics. The image statistics may be improved by acquiring the emission data for longer durations. However, the total time of acquiring the emission data is limited by the decay of radioactive isotope and by the inability of the patients to lie still for extended durations.
Further, the image quality may be improved by including time-of-flight (TOF) information for the emission data. The TOF information is the time difference in detection of annihilation photon pair. The TOF is proportional to a position of origin of the annihilation photon pair along the line of response between corresponding coincidence detectors. The emission data is stored in a frame to include TOF information. However, when the emission data is stored in a frame, the memory and/or storage requirements increase significantly.